1. Field
The present specification relates to Fresnel Incoherent Correlation Holography (FINCH).
2. Description of the Related Art
Ever since Fresnel Incoherent Correlation Holography (FINCH) (J. Rosen and G. Brooker, “Digital spatially incoherent Fresnel holography” Opt. Lett. 32, 912-914 (2007)) showed its potential for fluorescence microscopy (J. Rosen and G. Brooker, “Non-scanning motionless fluorescence three-dimensional holographic microscopy” Nat. Photonics 2, 190-195 (2008)), we have sought to perfect the technique into a useful high resolution 3D imaging method. The concept that a 3D image could be obtained from incoherent sources by a holographic process, without lasers, scanning or axial translation or the need to capture images at multiple planes of focus to create a 3D image is appealing. The field has now advanced as a result of additional work from our group (G. Brooker, N. Siegel, V. Wang, and J. Rosen, “Optimal resolution in Fresnel incoherent correlation holographic fluorescence microscopy,” Opt. Express 19, 5047-5062 (2011); J. Rosen, N. Siegel, and G. Brooker, “Theoretical and experimental demonstration of resolution beyond the Rayleigh limit by FINCH fluorescence microscopic imaging,” Opt. Express 19, 26249-26268 (2011); B. Katz, J. Rosen, R. Kelner, and G. Brooker, “Enhanced resolution and throughput of Fresnel incoherent correlation holography (FINCH) using dual diffractive lenses on a spatial light modulator (SLM),” Opt. Express 20, 9109-9121 (2012); N. Siegel, J. Rosen, and G. Brooker, “Reconstruction of objects above and below the objective focal plane with dimensional fidelity by FINCH fluorescence microscopy,” Opt. Express 20, 19822-19835 (2012)) and other laboratories (P. Bouchal, J. Kapitan, R. Chmelik, and Z. Bouchal, “Point spread function and two-point resolution in Fresnel incoherent correlation holography,” Opt. Express 19, 15603-15620 (2011); X. Lai, Y. Zhao, X. Lv, Z. Zhou, and S. Zeng, “Fluorescence holography with improved signal-to-noise ratio by near image plane recording,” Opt. Lett. 37, 2445-2447 (2012); O. Bouchal and Z. Bouchal, “Wide-field common-path incoherent correlation microscopy with a perfect overlapping of interfering beams,” J. Europ. Opt. Soc.—Rap. Pub. 8, 13011 (2013)) including the demonstration that the FINCH optical system is inherently super-resolving (J. Rosen, N. Siegel, and G. Brooker, “Theoretical and experimental demonstration of resolution beyond the Rayleigh limit by FINCH fluorescence microscopic imaging,” Opt. Express 19, 26249-26268 (2011).; B. Katz, J. Rosen, R. Kelner, and G. Brooker, “Enhanced resolution and throughput of Fresnel incoherent correlation holography (FINCH) using dual diffractive lenses on a spatial light modulator (SLM),” Opt. Express 20, 9109-9121 (2012); N. Siegel, J. Rosen, and G. Brooker, “Reconstruction of objects above and below the objective focal plane with dimensional fidelity by FINCH fluorescence microscopy,” Opt. Express 20, 19822-19835 (2012)) Recently it has been shown that the reason for this is that FINCH overcomes the Lagrange invariant (X. Lai, S. Zeng, X. Lv, J. Yuan, and L. Fu, “Violation of the Lagrange invariant in an optical imaging system,” Opt. Lett. 38, 1896-1898 (2013) [10]).
Common to all previous studies involving the FINCH technique has been the use of spatial light modulator (SLM) devices to act as in-line beam splitters to separate the reference and sample beams coincident within a single axis except for the system suggested by Kim (M. K. Kim, “Full color natural light holographic camera,” Opt. Express, 21, 9636-9642 (2013)) which operate like FINCH but are based on a Michelson-like interferometer without an SLM. Unfortunately this arrangement is difficult to setup, is sensitive to vibration since it is based upon a two optical beam interferometer, rather than the single beam FINCH concept in which both reference and sample beam paths traverse a coincident optical path. Furthermore the Kim approach has not been shown to produce high quality images.
SLM devices are usually liquid crystal deposited on a reflective semiconductor pixel matrix. Because of the reflective nature of the devices, they must be used at an angle to reflect the processed beam, complicating optical configurations. Furthermore, their resolution is dependent upon the pixel density of the devices and because they are pixelated, light is diffracted into many orders which significantly reduces light efficiency and results in unwanted image reflections. Even greater light loss is observed if they are used on axis with a beam splitting cube to try and overcome some of these limitations (G. Brooker, N. Siegel, V. Wang, and J. Rosen, “Optimal resolution in Fresnel incoherent correlation holographic fluorescence microscopy,” Opt. Express 19, 5047-5062 (2011); O. Bouchal and Z. Bouchal, “Wide-field common-path incoherent correlation microscopy with a perfect overlapping of interfering beams,” J. Europ. Opt. Soc.—Rap. Pub. 8, 13011 (2013)). Other image degrading characteristics include, for example, the small aperture size of the devices, astigmatic properties and their limited dynamic range. Thus SLM devices inherently reduce light throughput and fidelity, affecting the ultimate resolution of holograms and thus the reconstructed images.
In this specification, in order to overcome these limitations, the Applicants have invented a new high performance optical system for FINCH which operates in a straight line optical path with about 90% transmission efficiency in the creation of the sample and reference beams, is pixel free and devoid of other limitations of a SLM. The SLM is replaced in this new FINCH configuration with a polarization sensitive transmission liquid crystal GRIN lens (TLCGRIN) (N. Hashimoto and M. Kurihara, Proc. of SPIE 7232, 72320N-1-8 (2009)) in combination with an achromatic glass lens. This liquid crystal GRIN lens is combined with a glass lens to create, from each incoherent sample point, two converging, orthogonally polarized waves so that an in-line reference and sample beam could interfere and thus create a hologram. Since TLCGRIN lenses are polarization sensitive analog electro-optic devices which create high resolution lenses, we were able to adapt them to this new FINCH configuration and overcome the previous functional limitation of SLM based FINCH devices. In some versions of this arrangement a transmission liquid crystal Fresnel lens could be substituted for the TLCGRIN lens, however the TLCGRIN lenses are preferred because of their tunability and superior optical properties.